DEVONIC FISHES OF THE NEW YORK FORMATIONS 4 1 



plate. Abruptly truncated in front, and with linear lateral margins in the 

 anterior half, the posterolateral borders of the plate converge toward 

 the hinder extremity in a gently undulating curve. The under internal 

 surface of the plate is smooth without either a longitudinal ridge, pits or 

 transverse folds, such as sometimes occur towards the posterior end in other 

 species. The extreme width of the plate is slightly in excess of the total 

 length, which amounts to 4 centimeters in the type specimen. 



Owing to the favorable state of preservation of this interesting speci- 

 men it is possible to examine all of its characters. By a blow of the ham- 

 mer, which broke open the matrix, a portion of the bone substance was 

 splintered into fragments and lost. The remaining pieces, however, were 

 carefully collected, cemented together and embedded in a plaster mold 

 which was prepared from the impression left in the rock by the inferior 

 surface of the plate. Similarly, an impression of the tuberculated external 

 surface is preserved in the opposite counterpart. The distinctive characters 

 of the plate, which consist in its highly elevated form, prominent carina 

 and nature of the superficial ornament, are well illustrated in the figures 

 that are given of the bone itself and the impression of its inferior surface. 



The type of the species was collected from the sandstone beds exposed 

 on the Chapman Plantation in Aroostook county, Maine, sometimes referred 

 to as the Chapman sandstone. The invertebrate species accompanying this 

 fish constitute a fauna of early Devonic age, as abundantly confirmed by 

 the complete elaboration of the species.' The type specimen of A. 

 clarkei is preserved in the New York State Museum. 



Formation and locality. Chapman sandstone (Lower Devonic) ; Chap- 

 man Plantation, Aroostook county. Me. 



'Science, Dec. 28, 1901; Am. Ass'n Adv. Sci. Proc. 1901. 

 According to Clarke the evidence indicates an assemblage having a strong element 

 of affiliation with the Coblentzian (Lower Devonic) of the Rhine and certain identities 

 with the Helderberg and Oriskany of New York. This restudy of the fauna shows no 

 dependable relationship to the Siluric. 



